2. Field of Invention
The present invention relates to a backlight module and a liquid crystal display (LCD) including the same, and more particularly, to a backlight module having a heat conductive structure so as to reducing the non-uniformity phenomenon of display and liquid crystal display including thereof.
2. Description of Related Art
During data processing, an integrated circuit (IC) usually generates heat, and thus it has been quite an important factor for the design of electrical module regarding how to enhance the heat-dissipation design to increase the heat-dissipation efficacy, particularly in LCD industries. Since the data displaying speed is increasing daily, and the limitation of size (particularly for notebook computers) results in a very short distance between electrical components and optical elements in a LCD module, the high heat generated from the electrical components will affect locally the optical performance of an optical film of a backlight module, a light guide plate or liquid crystals in an array/cell.
With respect to a twisted nematic liquid crystal display (TN LCD), its transmittance shows a relationship of negative temperature coefficient with the change of temperature, i.e. the higher the temperature is, the lower the transmittance becomes. In addition, when the conditions between the LC cell and liquid crystals are different, the change of the transmittance will become more significant, thus making the phenomenon of transmittance lowered with increasing temperature more apparent.
In a LCD module, under certain display patterns requiring bigger loads, the electrical components on a printed circuit board (PCB) will cause the phenomenon of high temperature, wherein the temperature thereof can be more than 60° C. On the products having stricter requirements on the module size, such as a liquid crystal panel model of a notebook computer, a PCB is folded and fixed on a backlight module while in assembly, and for further saving space, electrical components on the PCB are disposed inwards and spaced from a reflection sheet at quite a small distance. Under this situation, when the heat generated from the electrical components is concentrated in the apparatus without any design of heat insulation or heat conduction, the liquid crystals therein will be caused to have the phenomenon of local high temperature, thus resulting in the local non-uniformity of display.
A conventional method for overcoming the aforementioned problem is to attach a heat-conductive metal plate on the back of the reflection sheet for uniformly distributing the high heat generated by the electrical components, thereby preventing the local transmittance of LC cell from being lowered by the heat concentrated on one certain point. However, due to the different heat expansion coefficients between the heat conductive plate and the reflection sheet, the heat-conductive plate directly attached to the reflection sheet will result in the local non-uniformity of display, and the heat-conductive plate attached will also cause the generation of a visible fringe or dark area of the display around the edge thereof, thus resulting in apparent bright lines shown on the display.